LVM2/liblvm lvm2app.h lvm_lv.c lvm_pv.c lvm_vg.c

LVM2/liblvm lvm2app.h lvm_lv.c lvm_pv.c lvm_vg.c

[wysochanski]

CVSROOT:	/cvs/lvm2
Module name:	LVM2
Changes by:	wysochanski at sourceware.org	2010-04-19 15:22:24

Modified files:
	liblvm         : lvm2app.h lvm_lv.c lvm_pv.c lvm_vg.c 

Log message:
	Use vg->vgmem to allocate vg/lv/pv string properties instead of dm_malloc/fr
	
	Everywhere else in the API the caller can rely on lvm2app taking care of
	memory allocation and free, so make the 'name' and 'uuid' properties of a
	vg/lv/pv use the vg handle to allocate memory.
	
	Signed-off-by: Dave Wysochanski <dwysocha@redhat.com>

Patches:
http://sourceware.org/cgi-bin/cvsweb.cgi/LVM2/liblvm/lvm2app.h.diff?cvsroot=lvm2&r1=1.14&r2=1.15
http://sourceware.org/cgi-bin/cvsweb.cgi/LVM2/liblvm/lvm_lv.c.diff?cvsroot=lvm2&r1=1.21&r2=1.22
http://sourceware.org/cgi-bin/cvsweb.cgi/LVM2/liblvm/lvm_pv.c.diff?cvsroot=lvm2&r1=1.10&r2=1.11
http://sourceware.org/cgi-bin/cvsweb.cgi/LVM2/liblvm/lvm_vg.c.diff?cvsroot=lvm2&r1=1.39&r2=1.40

--- LVM2/liblvm/lvm2app.h	2010/02/24 18:16:44	1.14
+++ LVM2/liblvm/lvm2app.h	2010/04/19 15:22:24	1.15
@@ -642,12 +642,12 @@
 uint64_t lvm_vg_get_seqno(const vg_t vg);
 
 /**
- * Get the current name of a volume group.
+ * Get the current uuid of a volume group.
  *
  * \memberof vg_t
  *
- * Memory is allocated using dm_malloc() and caller must free the memory
- * using dm_free().
+ * The memory allocated for the uuid is tied to the vg_t handle and will be
+ * released when lvm_vg_close() is called.
  *
  * \param   vg
  * VG handle obtained from lvm_vg_create or lvm_vg_open().
@@ -655,15 +655,15 @@
  * \return
  * Copy of the uuid string.
  */
-char *lvm_vg_get_uuid(const vg_t vg);
+const char *lvm_vg_get_uuid(const vg_t vg);
 
 /**
- * Get the current uuid of a volume group.
+ * Get the current name of a volume group.
  *
  * \memberof vg_t
  *
- * Memory is allocated using dm_malloc() and caller must free the memory
- * using dm_free().
+ * The memory allocated for the name is tied to the vg_t handle and will be
+ * released when lvm_vg_close() is called.
  *
  * \param   vg
  * VG handle obtained from lvm_vg_create or lvm_vg_open().
@@ -671,7 +671,7 @@
  * \return
  * Copy of the name.
  */
-char *lvm_vg_get_name(const vg_t vg);
+const char *lvm_vg_get_name(const vg_t vg);
 
 /**
  * Get the current size in bytes of a volume group.
@@ -783,7 +783,7 @@
  * \memberof vg_t
  *
  * The memory allocated for the list is tied to the vg_t handle and will be
- * released when lvm_vg_close is called.
+ * released when lvm_vg_close() is called.
  *
  * To process the list, use the dm_list iterator functions.  For example:
  *      vg_t vg;
@@ -896,7 +896,7 @@
  * \return
  * Copy of the uuid string.
  */
-char *lvm_lv_get_uuid(const lv_t lv);
+const char *lvm_lv_get_uuid(const lv_t lv);
 
 /**
  * Get the current uuid of a logical volume.
@@ -912,7 +912,7 @@
  * \return
  * Copy of the name.
  */
-char *lvm_lv_get_name(const lv_t lv);
+const char *lvm_lv_get_name(const lv_t lv);
 
 /**
  * Get the current size in bytes of a logical volume.
@@ -1001,7 +1001,7 @@
  * \memberof lv_t
  *
  * The memory allocated for the list is tied to the vg_t handle and will be
- * released when lvm_vg_close is called.
+ * released when lvm_vg_close() is called.
  *
  * To process the list, use the dm_list iterator functions.  For example:
  *      lv_t lv;
@@ -1057,8 +1057,8 @@
  *
  * \memberof pv_t
  *
- * Memory is allocated using dm_malloc() and caller must free the memory
- * using dm_free().
+ * The memory allocated for the uuid is tied to the vg_t handle and will be
+ * released when lvm_vg_close() is called.
  *
  * \param   pv
  * Physical volume handle.
@@ -1066,15 +1066,15 @@
  * \return
  * Copy of the uuid string.
  */
-char *lvm_pv_get_uuid(const pv_t pv);
+const char *lvm_pv_get_uuid(const pv_t pv);
 
 /**
  * Get the current name of a physical volume.
  *
  * \memberof pv_t
  *
- * Memory is allocated using dm_malloc() and caller must free the memory
- * using dm_free().
+ * The memory allocated for the uuid is tied to the vg_t handle and will be
+ * released when lvm_vg_close() is called.
  *
  * \param   pv
  * Physical volume handle.
@@ -1082,7 +1082,7 @@
  * \return
  * Copy of the name.
  */
-char *lvm_pv_get_name(const pv_t pv);
+const char *lvm_pv_get_name(const pv_t pv);
 
 /**
  * Get the current number of metadata areas in the physical volume.
--- LVM2/liblvm/lvm_lv.c	2010/03/25 18:22:05	1.21
+++ LVM2/liblvm/lvm_lv.c	2010/04/19 15:22:24	1.22
@@ -39,7 +39,7 @@
 	return SECTOR_SIZE * lv_size(lv);
 }
 
-char *lvm_lv_get_uuid(const lv_t lv)
+const char *lvm_lv_get_uuid(const lv_t lv)
 {
 	char uuid[64] __attribute((aligned(8)));
 
@@ -47,17 +47,13 @@
 		log_error(INTERNAL_ERROR "unable to convert uuid");
 		return NULL;
 	}
-	return strndup((const char *)uuid, 64);
+	return dm_pool_strndup(lv->vg->vgmem, (const char *)uuid, 64);
 }
 
-char *lvm_lv_get_name(const lv_t lv)
+const char *lvm_lv_get_name(const lv_t lv)
 {
-	char *name;
-
-	name = dm_malloc(NAME_LEN + 1);
-	strncpy(name, (const char *)lv->name, NAME_LEN);
-	name[NAME_LEN] = '\0';
-	return name;
+	return dm_pool_strndup(lv->vg->vgmem, (const char *)lv->name,
+			       NAME_LEN+1);
 }
 
 uint64_t lvm_lv_is_active(const lv_t lv)
--- LVM2/liblvm/lvm_pv.c	2010/03/25 18:22:05	1.10
+++ LVM2/liblvm/lvm_pv.c	2010/04/19 15:22:24	1.11
@@ -17,7 +17,7 @@
 #include "metadata-exported.h"
 #include "lvm-string.h"
 
-char *lvm_pv_get_uuid(const pv_t pv)
+const char *lvm_pv_get_uuid(const pv_t pv)
 {
 	char uuid[64] __attribute((aligned(8)));
 
@@ -25,17 +25,13 @@
 		log_error(INTERNAL_ERROR "Unable to convert uuid");
 		return NULL;
 	}
-	return strndup((const char *)uuid, 64);
+	return dm_pool_strndup(pv->vg->vgmem, (const char *)uuid, 64);
 }
 
-char *lvm_pv_get_name(const pv_t pv)
+const char *lvm_pv_get_name(const pv_t pv)
 {
-	char *name;
-
-	name = dm_malloc(NAME_LEN + 1);
-	strncpy(name, (const char *)pv_dev_name(pv), NAME_LEN);
-	name[NAME_LEN] = '\0';
-	return name;
+	return dm_pool_strndup(pv->vg->vgmem,
+			       (const char *)pv_dev_name(pv), NAME_LEN + 1);
 }
 
 uint64_t lvm_pv_get_mda_count(const pv_t pv)
--- LVM2/liblvm/lvm_vg.c	2010/03/25 18:22:05	1.39
+++ LVM2/liblvm/lvm_vg.c	2010/04/19 15:22:24	1.40
@@ -328,7 +328,7 @@
 	return vg_max_lv(vg);
 }
 
-char *lvm_vg_get_uuid(const vg_t vg)
+const char *lvm_vg_get_uuid(const vg_t vg)
 {
 	char uuid[64] __attribute((aligned(8)));
 
@@ -336,17 +336,12 @@
 		log_error(INTERNAL_ERROR "Unable to convert uuid");
 		return NULL;
 	}
-	return strndup((const char *)uuid, 64);
+	return dm_pool_strndup(vg->vgmem, (const char *)uuid, 64);
 }
 
-char *lvm_vg_get_name(const vg_t vg)
+const char *lvm_vg_get_name(const vg_t vg)
 {
-	char *name;
-
-	name = dm_malloc(NAME_LEN + 1);
-	strncpy(name, (const char *)vg->name, NAME_LEN);
-	name[NAME_LEN] = '\0';
-	return name;
+	return dm_pool_strndup(vg->vgmem, (const char *)vg->name, NAME_LEN+1);
 }
 
 struct dm_list *lvm_list_vg_names(lvm_t libh)

LVM2/liblvm lvm2app.h lvm_lv.c lvm_pv.c lvm_vg.c

[Zdenek Kabelac]

On 19.4.2010 17:22, wysochanski at sourceware.org wrote:
> CVSROOT:	/cvs/lvm2
> Module name:	LVM2
> Changes by:	wysochanski at sourceware.org	2010-04-19 15:22:24
> 
> Modified files:
> 	liblvm         : lvm2app.h lvm_lv.c lvm_pv.c lvm_vg.c 
> 
> Log message:
> 	Use vg->vgmem to allocate vg/lv/pv string properties instead of dm_malloc/fr
> 	
> 	Everywhere else in the API the caller can rely on lvm2app taking care of
> 	memory allocation and free, so make the 'name' and 'uuid' properties of a
> 	vg/lv/pv use the vg handle to allocate memory.
> 	
> 	Signed-off-by: Dave Wysochanski <dwysocha@redhat.com>

> -char *lvm_vg_get_name(const vg_t vg)
> +const char *lvm_vg_get_name(const vg_t vg)
>  {
> -	char *name;
> -
> -	name = dm_malloc(NAME_LEN + 1);
> -	strncpy(name, (const char *)vg->name, NAME_LEN);
> -	name[NAME_LEN] = '\0';
> -	return name;
> +	return dm_pool_strndup(vg->vgmem, (const char *)vg->name, NAME_LEN+1);
>  }


Either we should return   const char*  return vg->name;
or we should  char* return strdup(vg->name) and user could do whatever he
wants to do with the string.

I'd prefer 1.) for efficiency, but I don't see any point in current code.
Usually user wants to make a quick check for something - he will use const
char*, or he want to keep it for later and he fill duplicate string with his
own memory allocation routines (i.e. C++ new.... )

Zdenek

LVM2/liblvm lvm2app.h lvm_lv.c lvm_pv.c lvm_vg.c

[Alasdair G Kergon]

On Mon, Apr 19, 2010 at 05:34:04PM +0200, Zdenek Kabelac wrote:
> Either we should return   const char*  return vg->name;

But then we have to guarantee that vg->name remains const - which we are
unable to do.  (We can't impose limits on vgrename.)

Alasdair

LVM2/liblvm lvm2app.h lvm_lv.c lvm_pv.c lvm_vg.c

[Zdenek Kabelac]

On 19.4.2010 19:06, Alasdair G Kergon wrote:
> On Mon, Apr 19, 2010 at 05:34:04PM +0200, Zdenek Kabelac wrote:
>> Either we should return   const char*  return vg->name;
> 
> But then we have to guarantee that vg->name remains const - which we are
> unable to do.  (We can't impose limits on vgrename.)
> 

I think we may state, that until next call of any lvm library function pointer
remains valid. Thus if user needs it for something later - he needs to make a
local copy.

We may be nicer if we list functions which could change this pointer (i.e. I
wouldn't expect any *_get_* function could ever change it) - but I think it's
not needed - major use case would be to check value for something
and eventually copy somewhere - thus const char* is perfectly usable in this
case. So I think any const char* is valid between lvm calls - and if they are
valid after - it's just pure luck....

Zdenek

LVM2/liblvm lvm2app.h lvm_lv.c lvm_pv.c lvm_vg.c

[Alasdair G Kergon]

On Mon, Apr 19, 2010 at 08:38:16PM +0200, Zdenek Kabelac wrote:
> wouldn't expect any *_get_* function could ever change it

Yes it could - the vgrename might have been run on a different machine in the
cluster.

Alasdair

LVM2/liblvm lvm2app.h lvm_lv.c lvm_pv.c lvm_vg.c

[Dave Wysochanski]

On Mon, 2010-04-19 at 17:34 +0200, Zdenek Kabelac wrote:
> On 19.4.2010 17:22, wysochanski at sourceware.org wrote:
> > CVSROOT:	/cvs/lvm2
> > Module name:	LVM2
> > Changes by:	wysochanski at sourceware.org	2010-04-19 15:22:24
> > 
> > Modified files:
> > 	liblvm         : lvm2app.h lvm_lv.c lvm_pv.c lvm_vg.c 
> > 
> > Log message:
> > 	Use vg->vgmem to allocate vg/lv/pv string properties instead of dm_malloc/fr
> > 	
> > 	Everywhere else in the API the caller can rely on lvm2app taking care of
> > 	memory allocation and free, so make the 'name' and 'uuid' properties of a
> > 	vg/lv/pv use the vg handle to allocate memory.
> > 	
> > 	Signed-off-by: Dave Wysochanski <dwysocha@redhat.com>
> 
> > -char *lvm_vg_get_name(const vg_t vg)
> > +const char *lvm_vg_get_name(const vg_t vg)
> >  {
> > -	char *name;
> > -
> > -	name = dm_malloc(NAME_LEN + 1);
> > -	strncpy(name, (const char *)vg->name, NAME_LEN);
> > -	name[NAME_LEN] = '\0';
> > -	return name;
> > +	return dm_pool_strndup(vg->vgmem, (const char *)vg->name, NAME_LEN+1);
> >  }
> 
> 
> Either we should return   const char*  return vg->name;
> or we should  char* return strdup(vg->name) and user could do whatever he
> wants to do with the string.
> 
> I'd prefer 1.) for efficiency, but I don't see any point in current code.
> Usually user wants to make a quick check for something - he will use const
> char*, or he want to keep it for later and he fill duplicate string with his
> own memory allocation routines (i.e. C++ new.... )
> 

I thought I answered this in my other mail, but you never responded.

I guess you are not as concerned about a misbehaving application as I
am.  Returning pointers to internal LVM data seems dangerous to me, but
perhaps I'm overly paranoid.

Indeed, 'const' should be enough to tell the application "this is a
snapshot of the present state, don't modify it".  But what if he does -
then we have a potential for corrupt metadata.  I'd like to take #1
approach, but it just doesn't seem safe.

If you copy memory but don't use 'const', then I would think this sends
the wrong message to applications using the API.